In the prior art, whether for a micro speaker or a large speaker, the problem which limits the maximum power application of the product when operating in low frequency conditions lies in that: under a large power, the voice coil operating in low frequency conditions produces an excessive displacement which will cause abrupt raising distortion and even causes an obvious collision problem between the voice coil and the magnetic circuit system, which will cause mechanical damage to the product system.
For this problem, the current solution is to adopt an intelligent power amplification control unit to control the power of the speaker product. The actual displacement of the vibration system of the speaker is “deduced” according to input information (such as voltage) and monitored information (such as current) and physical parameters of the speaker. The power of the speaker product is reduced when the actual displacement exceeds a preset threshold.
However, the deduction of the actual displacement by the intelligent power amplification control unit is still built on a hypothetical theoretical model which still has certain differences from the actual product. In addition, for micro speakers produced in batch, there are always some deviations in the physical parameters of the speakers and 100% consistence cannot be realized. The above reason causes that it is difficult for the deduction of the actual displacement by the intelligent power amplification control unit to reflect the real displacement of each speaker product precisely and in real time.